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PLoS Pathog. 2014 Nov 6;10(11):e1004479. doi: 10.1371/journal.ppat.1004479. eCollection 2014 Nov.

The Pseudomonas aeruginosa type III translocon is required for biofilm formation at the epithelial barrier.

Author information

1
Department of Pediatrics, University of California San Francisco, San Francisco, California, United States of America.
2
Department of Microbiology-Immunology, Northwestern University, Chicago, Illinois, United States of America.
3
Costern Biofilm Center, Department of International Health, Immunology and Microbiology, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark.
4
Institut Pasteur de Montevideo, Montevideo, Uruguay.
5
Costern Biofilm Center, Department of International Health, Immunology and Microbiology, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark; Singapore Centre on Environmental Life Sciences Engineering, Nanyang Technological University, Singapore.
6
Department of Microbiology and Immunology, University of California San Francisco, San Francisco, California, United States of America; Department of Medicine, University of California San Francisco, San Francisco, California, United States of America.

Abstract

Clinical infections by Pseudomonas aeruginosa, a deadly Gram-negative, opportunistic pathogen of immunocompromised hosts, often involve the formation of antibiotic-resistant biofilms. Although biofilm formation has been extensively studied in vitro on glass or plastic surfaces, much less is known about biofilm formation at the epithelial barrier. We have previously shown that when added to the apical surface of polarized epithelial cells, P. aeruginosa rapidly forms cell-associated aggregates within 60 minutes of infection. By confocal microscopy we now show that cell-associated aggregates exhibit key characteristics of biofilms, including the presence of extracellular matrix and increased resistance to antibiotics compared to planktonic bacteria. Using isogenic mutants in the type III secretion system, we found that the translocon, but not the effectors themselves, were required for cell-associated aggregation on the surface of polarized epithelial cells and at early time points in a murine model of acute pneumonia. In contrast, the translocon was not required for aggregation on abiotic surfaces, suggesting a novel function for the type III secretion system during cell-associated aggregation. Supernatants from epithelial cells infected with wild-type bacteria or from cells treated with the pore-forming toxin streptolysin O could rescue aggregate formation in a type III secretion mutant, indicating that cell-associated aggregation requires one or more host cell factors. Our results suggest a previously unappreciated function for the type III translocon in the formation of P. aeruginosa biofilms at the epithelial barrier and demonstrate that biofilms may form at early time points of infection.

Comment in

PMID:
25375398
PMCID:
PMC4223071
DOI:
10.1371/journal.ppat.1004479
[Indexed for MEDLINE]
Free PMC Article

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